misc styles-related changes

* Drop all language properties from templates and get the language info
  only from the input DTBook.
* Add missing default-styles
* Some refactoring
Definition list related changes:

* move page numbers inside dl to after the dl
* support non-paired dt/dd
fix for notes inside tables
Support for dtb:prodnote
set image_dpi to 600
For math show both the 2D formula and the ASCIIMath expression
Give more elements a text or paragraph style

* prodnote
* th
* caption
* pagenum
* span.exercisenumber
* span.exercisepart
* sub
* sup
* strong
* em
* dt
* note
* annotation
* cite
* q
* author
* title
* acronym
* abbr
* kbd
* code
* samp
* linenum
Proper whitespace handling based on xml:space
Don't embed images
Offer choice between MS Word/LibreOffice default list styles
Update template (text styles)